Silicon wafers used in electronic devices are typically prepared from a single crystal silicon ingot that is first sliced into thin wafers using a diamond saw and then ground to remove surface imperfections arising from the sawing process. The silicon wafers then typically require a final polishing step to provide surfaces having very low surface roughness before they are acceptable for use in electronic devices.
Current methods of performing final polishing of silicon wafers often employ polishing compositions containing silica as an abrasive in an aqueous carrier and further comprising additives such as amines or quaternary ammonium salts as polishing rate enhancers. However, conventional polishing compositions for silicon wafers generally require over 10 minutes of polishing in order to remove 10-20 microns of silica. Polishing compositions are desired that can be used to polish silicon more quickly to improve throughput and more effectively utilize production capacity.
In addition, it is desirable to ship polishing compositions as concentrates (e.g., to reduce shipping volume and weight), which concentrates are then diluted by the user prior to polishing. However, conventional silicon polishing compositions exhibit colloidal instability at high concentrations, leading to difficulties in the redispersion of abrasive particles on dilution. Thus, there remains an important need in the art for improved polishing compositions for silicon wafers.